Go Structs: Difference between revisions
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The <tt>struct</tt>s can be declare at package level or inside a function. | |||
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Revision as of 04:09, 30 March 2016
Internal
Overview
A struct is a user-defined type that contains named fields. structs can also have methods associated with them.
- Can structs only be declared in packages, or in functions too?
- Are all users can define (in terms of types) structs, or there are other user-defined types?
Definition
The struct type definition is introduced by the type keyword, to indicated that this is a user-defined type, followed by the type name and the keyword struct. Each field has a name and a type.
type myStruct struct { i int s string }
Fields with the same types can be collapsed:
type myStruct struct { ... i, j, k int ... }
The structs can be declare at package level or inside a function.
Initialization
Long Variable Declaration
var ms myStruct
If no explicit initialization follows, all the struct's fields are initialized with their zero value.
Short Variable Declaration
Literal
Struct literal initialization:
ms := myStruct{i: 5, s: "something"}
There is a shorter struct literal where the name of the fields are omitted, provided that the order is maintained:
ms := myStruct{5, "something"}
new()
new() initialization:
msPtr := new(myStruct)
Note new() returns a pointer to the structure and not the structure itself.
Fields
Fields can be access with the . operator.
Note that the . operator works with a regular struct variable as well as with a pointer to a struct: the compiler knows how to compensate for both of these cases.
ms := myStruct{1, "s"} msPtr := new(myStruct) // valid: ms.i // valid: msPtr.i
As long as the enclosing struct type is exported by a package, all fields are exported, regardless of their capitalization.